The present invention relates to an apparatus and method for demodulating an input signal modulated from a reference signal and a data signal, and more particularly, to an apparatus and method for efficiently demodulating a saw tooth wobble (STW) signal modulated from a wobble signal and a data signal in a BD (Blu-ray Disk).
In general, the STW signal in the BD is formed by a sinusoidal signal having a wobble frequency (i.e. the wobble signal) added to another sinusoidal signal having a data frequency (i.e. the data signal), wherein the data frequency is twice as greater as the wobble frequency. Please refer to FIG. 1 in conjunction with FIG. 2. FIG. 1 is a simplified diagram showing an STW signal modulated from the wobble signal and a data 1 signal having a first data frequency (i.e. an STW data 1 signal), and FIG. 2 is a simplified diagram showing another STW signal modulated from the wobble signal and a data 0 signal having a second data frequency (i.e. an STW data 0 signal).
Based on the signal characteristics depicted in FIG. 1 and FIG. 2, including phase and frequency, conventional apparatus and methods usually utilize a band-pass filter whose center frequency is at the data frequency (i.e. the double wobble frequency), or multiply the input signal with the data frequency and then extract the data signal. However, the band-pass filter and the multiplier are very expensive, and therefore it is quite difficult to reduce the cost of the conventional apparatus and methods for demodulating the STW signal in the BD.